This video is brought to you by Squarespace. George A. Romero’s 1968 thriller Night of the Living Dead started what many refer to as the “zombie craze”, and for good reason. Romero’s terrifying film blends the inevitability of sickness, the inscrutability of the unknown, and our primal fear of becoming prey into a 2-hour horror romp through an undead wasteland. So what if I told you that an infection exists that can wrench control over your mind and drive you as if you were a big fleshy meat robot? A 29-year old man came to the Isfahan University of Medical Sciences and Health Services, after undergoing a loss of central vision, sensitivity to light, redness, and pain in his right eye. He made clear that he didn’t have any underlying health conditions, any genetic predispositions to eye disease, nor any major changes in his lifestyle. So what could be the problem? Something terrible probably. Upon examination, doctors found that his left eye was operating properly, however his right eye was struggling to keep up. They also found a macular edema—a buildup of fluid in the retina, and pressure exerting on both of his eyes. After a closer look though, they found what they call an “elevated, creamy retinal lesion” in his right eye. Please don’t call it “creamy” again. Creamy. Ugh. After a series of tests, doctors diagnosed him with Ocular Toxoplasmosis. The diagnosis wasn’t definitive, but they ran him on a course of meds just in case. This was to no avail, as 6 months later the patient returned with worsening vision that couldn’t be fixed with meds or a pinhole aperture. What’s a pinhole aperture? They’re basically a pair of glasses with sheets of dotted material instead of corrective lenses. You might be more familiar with the solar eclipse camera. They pretty much just limit and direct the light to help those with photosensitivity. In this case, it didn’t work, so doctors needed to resort to more... invasive solutions. What do you mean by invasive? They decided that they needed to perform a lensectomy. A lensectomy is a procedure where ophthalmologists will cut a small slit into the wall of the eye, and then, either by using soundwaves or vibrations, break up the material that the optical lens is made of. After the lens is broken, the surgeon will use a micro vacuum to suck out any shards of lens, and then rinse out the eye with a saline solution before replacing the lens with a man made alternative. In the end, doctors were unable to correct his vision, leaving him with an “uncorrectable retinal fibrosis with a total closed funnel traction retinal detachment with shortening and fibrosis”. Which is like, the fanciest way to say that his retina was all scarred to hell, and had peeled off the back of his eye like old wallpaper. Oh okay. But what happens after that? Retinal detachment usually causes a sudden spike in those little floaters you see in your vision, flashes of light, reduced peripheral vision, and a curtain-esque shadow over your field of vision. Hey, that’s not so bad. Oh yeah, but retinal detachment can lead to permanent vision loss. So, blindness in one or both eyes. Nevermind, that is so bad. The really unfortunate thing about our case is that he was only 29 years old, and losing your vision that early in life is hard to overcome. Doctors’ initial diagnosis of our case study with ocular toxoplasmosis, which led to all of his subsequent health issues. So maybe people aren’t turning into zombies, so what’s actually going on here? Toxoplasmosis is the infection caused by a single-celled parasite called Toxoplasma gondii. The parasite is found all over the world, and according to the CDC, up to 40 million Americans could currently be infected. Symptoms usually appear flu-like, meaning soreness in the lymph nodes, muscle aches, and pains that last longer than a month or two. Severe toxoplasmosis can cause damage to the eyes, brain, and other organs, but the majority of individuals infected with T. gondii are asymptomatic, meaning that they don’t show any symptoms at all. In fact, many healthy adults can be infected for their entire lives and never know, since their immune systems will ensure they never become sick from the infection. What we saw in our case was an acute form of ocular toxoplasmosis, which is pretty much just a regular infection of T. gondii, except it’s in the eyes. Ha, “T. Gondi-eyes” Still gross. Yeah, sorry. Symptoms include a reduction in visual acuity, sensitivity to bright light, and redness. In severe cases however, Ocular Toxoplasmosis can lead to permanent blindness or significant loss of vision. It’s actually easier to get infected by T. gondii than you think. If you have a cat, or spend time with cats, then you’re at risk. Brew, really think about what you’re gonna say next, and think about how you could be hurtin my cat loving feelings. Don’t worry, Grill. It’s just that the only definitive hosts for T. gondii are members of the family Felidae, or, as they’re also known, cats! A definitive host is the creature in which a parasite reaches its final form. In other words, the creature where the parasite will finish its lifecycle and reproduce. So it’s not like cats are actively trying to kill us. One of the major ways T. gondii gets into human hosts is through cat feces. These parasites will shed oocysts, or eggs, into cat feces, and they can get into our bodies if we don’t properly wash after cleaning a litterbox. For example, you clean a litter box, you rinse your hands, then you touch the steak you were making for dinner, and bing bang boom, you’re hosting a parasite. Another form of transmission is similar to other foodborne illnesses. The parasite gets into the food supply via infected cattle, or because someone involved in the production didn’t wash their hands.. For example, there’s a barn cat at a cattle ranch. The cat does its business in the field where the cattle grazes and infects one or more of them. When they are slaughtered, the tainted meat can get into stores, and eventually into our kitchens. T. gondii can also linger in water, and it usually gets there the same way it gets into food supplies. So a cat took a s#$% in the creek, and now I’m infected. Exactly! Wonderful. So only drinking clean water, or thoroughly boiling water before you drink it can ensure that you’re not inadvertently sipping on some delicious cat parasites. The last way T. gondii can infect you is intravenously. If you get a blood transfusion, or organ donation from someone infected by T. gondii, then obviously you’ll get it from them. It is also possible for pregnant women who are infected with T. gondii, to pass on the infection transplacentally to their developing fetus. This is a particular health risk as babies typically have less than fantastic immune systems. Get a functioning immune system, scrub. To be fair, Grill. Babies aren’t the only ones with weaker immune systems. As I said earlier, the majority of people infected with T. gondii are asymptomatic, and can remain infected for their entire lives, so those at risk are usually those with compromised immune functions. This includes individuals who are HIV positive, those undergoing treatments like radiotherapy and chemotherapy, people receiving steroids or immunosuppressant drugs, and, as I mentioned a moment ago, newborns. Toxoplasmosis is only a problem for healthy individuals when they’re pregnant, and when toxoplasmosis is severe enough to experience the symptoms mentioned earlier. Just practice proper handwashing, like you should, and if you’re pregnant or immunocompromised avoid changing cat litter. I can’t stand these things! Imagine a life form growing inside of you, slithering around, feeding off of you. Disgusting. Woah woah woah, hold the phone there big guy, you don’t have to talk smack about all forms of microbial symbiosis! There are all sorts of beneficial symbiotic relationships in nature! ...Come again? Like, what about all of the Bifidobacteria bros we have hanging around our intestinal tract? They help break down the food we eat! You know what Grill, sometimes it’s like you don’t even read my blog! I’m sorry! Yeesh, I didn’t know this was so import-wait how long have you had a blog? Four minutes? Maybe five—it felt like even less! But you know what, all that’s thanks to Squarespace! All I have to do is drag and drop my favorite pics and vids, pick a template, and presto! Just like that, you get “Simply Symbiotic” where I post all of my favorite examples of homies making homes out of homies! Such as the live probiotics found in fermented foods like cheese and yogurt! First cats, now my Yeegurt!!? Must they take everything I love!? You know what I love? How easy it is to have visitors share my content across their favorite social media platforms! If peeps are like “Ayy Yo, Chill! I love B. Animalis! and how they help me digest things so good.” Then they can spread the word with the click of a button! And look look! I can even customize the button! I made it look like Bean! Represent, Micro-homie! That doesn’t change the fact that these things are living inside of me, taking what’s mine! Rent free no less! Yeah who would ever do that. Well I don’t know what rent is, but if it involves money then all the more reason to sign up! Squarespace is affordable, convenient, and allows you to make websites without being a wizard, which is how I assume websites are made. You gotta be a wizard. And here at Simply Symbiotic we’re happy to announce that if you sign up now, we can get you 10% off of your first purchase off a website or domain! Cause we got you, boo! I’m sorry Chill but they’ve partnered with our channel, not your very cool blog. Well this is the first that Chill corp is hearing about this. Just head on over to “Squarespace.com/BREW” to get started. Well, I gotta hand it to ya. Sometimes, these micro monsters can be beneficial... They can take whatever they want from me, I’ll still be Grill! Not even a parasite could change me or my personality. Umm... Why ya looking at me like that right now? Oh GOD NO- The majority of human hosts won’t experience any of the symptoms, nor will the infection pose any serious threat to their health, but it has some tricks up it’s tiny microscopic sleeve to move from host to host. Researcher Hannah J. Johnson in a study with the American Society for Microbiology, found that rats infected with T. gondii exhibited a variety of personality and behavior changes that would be detrimental to survival in the wild. Scientists found that rats, both in clinical trials and those observed in the wild, struggled with memory tests significantly more if they were infected with the parasite. Likewise, they also found that infected rats displayed motor abnormalities in comparison to control populations, that is, infected rats were both more and less active than uninfected rats. Finally, it was also found that infected rats showed a diminished fear response in three ways. One, they were less averse to the scent of cat urine, one of their major predators, two, they showed a decreased fear of open spaces, and three, they were more likely to eat foods they hadn’t encountered before. Johnson offers possible explanations. She notes that “Decreased fear, especially to cat urine, has been postulated to increase the chance of predation of rodents by the definitive host, thus offering a potentially plausible reason for T. gondii infection to alter this behavior”. Essentially, the parasite overrides the rats’ basic survival instincts. If a rat were to constantly stand in the open, eat foods it had never seen before, and hang around where cats go to the bathroom, it might not survive that long, right? However, Johnson also adds, that “most studies report a mix of both positive and negative results” so a variety of factors could contribute to their findings. So, like a zombie virus, T. gondii will wreak havoc on the lives of lowly rats, driving them forward in a slow march toward death, but what about in humans? Johnson brings up over 200 papers that found those with antibodies to this parasite displayed “increased aggression, increased risk for motor vehicle accidents, decreased reaction time, and excessive ethanol consumption”. Essentially, infected individuals were shown to be less risk averse than uninfected control groups. Johnson notes that these behaviour changes have been accessed through the rodent model and arguments have been made to explain it. According to researcher Jaroslav Flegr, “Humans are dead-end hosts for T. gondii”, since it’s pretty unlikely that we’ll be eaten by a cat, however “parasites are not aware that they have entered dead-end hosts, so they are likely to exert whatever effects they do in any host”. The idea is that the same forces T. gondii use to get rodents killed and eaten, is likewise being used on us as well. The difference is that Humans don’t have many predators anymore. You know, outside of themselves. Interestingly enough, they even found that infected men were more likely to attend studies wearing wrinkled clothing, while women were more likely to wear formal clothing. Participants were also asked to drink an unidentified liquid, which found that infected women were generally more trusting, as they were more likely to drink it than infected men and uninfected populations. It was seen in multiple studies that “There was a different effect of the latent toxoplasmosis infection on women and men in all four behavioural composite variables.” These variables being: relationships, self-control, clothes tidiness, and mistrust. It is possible however, that these personality changes are not actually caused by the infection, and the idea is just media hype. For example, there is a relationship between infected populations and higher testosterone levels. It’s possible that high levels of testosterone make one more susceptible to infection, or that the infection increases testosterone in order to accomplish its goals. Flegr also mentions that rates of T. gondii infections are higher in rural areas of developing countries where clean water and education systems aren’t as robust. Ok, so T. gondii might not be the zombie Cordyceps fungus like from The Last of Us, but it could still be affecting us! Fortunately, unless you have a less than ideal immune system, you’re probably not going to experience any problems. Let alone turn into a flesh craving monster. It’s likely that this parasite can and is changing the way you behave. Whether we can attribute all the data we found on personality changes to the parasite itself, or if these changes are even noticeable for the infected individual. Oh also, be nice to cats. All species have diseases and parasites. It’s not their fault that something evolved in them, just as it’s not a single group’s fault that a new illness popped up around them. The moral of the story is that hand washing is important, just as proper food handling is important. Just washing your hands can ensure that you stay out of T. gondii’s para-sights. Oh God. Come on. That one was good, come on.
